1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a high voltage integrated circuit.
2. Description of the Background Art
A high voltage integrated circuit (HVIC) is a device indispensable for achieving great functionality and cost reduction in the field of mechatronics including motor control.
For instance, an HVIC is employed as a gate driver in a power transistor such as an IGBT (Integrated Gate Bipolar Transistor) used for performing bridge rectification of a power line. In this HVIC, when a high side IGBT and a low side IGBT are brought into an on state at the same time (which is called a “shoot-through” phenomenon), short-circuit occurs between arms (power lines) to cause a large current to flow into the IGBTs, which are therefore damaged.
To prevent this, the HVIC is controlled such that a high side gate driver output and a low side gate driver output are complementarily outputted. However, since the gate driver outputs are not monitored in practice, the high side IGBT is short-circuited in the case where a potential at a node between the high side IGBT and low side IGBT (hereinafter referred to as “potential VS”) is short-circuited to a ground potential (GND) (i.e., ground-fault occurs) due to failure in loads or the like while the high side gate driver continues outputting (i.e., while the high side IGBT is in an ON state). Therefore, the high side IGBT needs to be turned off immediately, however, the HVIC is incapable of determining that the potential VS has become GND, and therefore causes the high side gate driver to continue outputting.
To prevent this, simply saying, the potential VS may be monitored. However, the potential VS usually reaches several hundred volts. Thus, it is impossible to monitor the potential VS within the HVIC.
For instance, Japanese Patent Application Laid-Open No. 9-172358 (1997) discloses detecting overcurrent in the case where an emitter terminal of a high side IGBT is short-circuited to GND, thereby controlling the high side IGBT on the basis of a detection signal (see columns 6–7, FIGS. 1–3). With this method, however, a certain period of time is required until a control signal is applied to the high side IGBT, during which short-circuit continues. Therefore, the high side IGBT needs to have resistance to a short-circuit state for a certain period of time, which is a contributing factor responsible for increase in manufacturing costs.